Communication method and device in wireless LAN supporting emlsr

Abstract

A communication method and device in a wireless LAN supporting EMLSR are disclosed. A method of a first device comprises the steps of: transmitting a first frame to a second device on a primary link; and if a second frame that is a response to the first frame is not received from the second device on the primary link, performing communication with the second device on an auxiliary link, wherein each of the first device and the second device supports communication in multiple links including the primary link and the auxiliary link.

Description

Communication method and device in a wireless LAN supporting EMLSR

[0001] The present disclosure relates to wireless local area network (WLAN) communication technology, and more particularly, to communication technology in a wireless LAN supporting enhanced multi-link single-radio (EMLSR).

[0002] With the recent proliferation of mobile devices, Wireless Local Area Network (WLAN) technology, which can provide fast wireless communication services to these devices, is attracting significant attention. WLAN technology utilizes short-range wireless communication technology to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly access the Internet.

[0003] As applications requiring higher throughput and real-time transmission arise, the IEEE 802.11be standard, an Extreme High Throughput (EHT) wireless LAN technology, is being developed. The goal of the IEEE 802.11be standard may support a high throughput of 30 Gbps. The IEEE 802.11be standard may support technologies for reducing transmission delay. In addition, the IEEE 802.11be standard may support a wider frequency bandwidth (e.g., 320 MHz bandwidth), multi-link transmission and aggregation operation including operation using multiple bands, multi-AP (Access Point) transmission operation, and / or efficient retransmission operation (e.g., Hybrid Automatic Repeat Request (HARQ) operation).

[0004] However, since multi-link operation is an operation that is not defined in the existing wireless LAN standard, detailed operation definition may be required depending on the environment in which multi-link operation is performed. In particular, devices that support enhanced multi-link single radio (EMLSR) operation (e.g., STA (station), AP (access point), MLD (multi-link device)) can wait for reception on multiple links. Devices that support EMLSR operation may be referred to as EMLSR devices.

[0005] When an EMLSR device initiates a frame transmission / reception operation on a single link, the EMLSR device can only operate on the single link. In other words, the EMLSR device cannot perform frame transmission / reception operations on other links while performing frame transmission / reception operations on a single link. Interference may occur between multiple links. Transmission on one link may cause interference on other link(s). Due to the interference, additional detailed operations for EMLSR operation may be required. Depending on the additional detailed operations of the EMLSR, detailed operations for direct communication (e.g., scheduling for direct communication) on multiple links may be required.

[0006] Meanwhile, the technology that serves as the background for the invention is written to promote understanding of the background for the invention, and may include content that is not a prior art already known to a person with ordinary skill in the field to which the technology belongs.

[0007] The purpose of the present disclosure to solve the above problems is to provide a method and device for communication in a wireless LAN supporting enhanced multi-link single-radio (EMLSR).

[0008] A method of a first device according to embodiments of the present disclosure for achieving the above object includes the steps of transmitting a first frame to a second device on a primary link, and performing communication with the second device on a secondary link if a second frame in response to the first frame is not received from the second device on the primary link, wherein each of the first device and the second device supports communication on multiple links including the primary link and the secondary link.

[0009] If the second frame, which is a response to the first frame, is not received from the second device in the primary link, the state of the primary link may be determined to be an interference state or a busy state.

[0010] The method of the first device may further include the steps of transmitting the first frame to the second device on the auxiliary link, and receiving the second frame, which is a response to the first frame, from the second device on the auxiliary link, wherein the first frame may be transmitted simultaneously on the primary link and the auxiliary link, or transmission of the first frame on the auxiliary link may be performed when the second frame, which is a response to the first frame, is not received on the primary link.

[0011] The second frame received on the auxiliary link may include information indicating that the second device uses the auxiliary link instead of the primary link.

[0012] The second frame received on the auxiliary link may include information indicating a time at which the second device operates on the auxiliary link, and communication between the first device and the second device on the auxiliary link may be performed within the time indicated by the second frame.

[0013] The first frame may be a request to send (RTS) frame, and the second frame may be a clear to send (CTS) frame.

[0014] A method of a second device according to embodiments of the present disclosure for achieving the above object includes the steps of: detecting interference in a primary link; determining to perform communication in a secondary link when interference is detected in the primary link; receiving a first frame from a first device in the secondary link; and transmitting a second frame in response to the first frame in the secondary link to the first device, wherein each of the first device and the second device supports communication in multiple links including the primary link and the secondary link.

[0015] In the above main link, the interference can be detected based on CCA or OBSS transmission.

[0016] The second frame may include information indicating that the second device uses the auxiliary link instead of the primary link.

[0017] The second frame may include information indicating a time at which the second device operates on the auxiliary link, and communication between the first device and the second device on the auxiliary link may be performed within the time indicated by the second frame.

[0018] The first frame may be an RTS frame, and the second frame may be a CTS frame.

[0019] According to embodiments of the present disclosure for achieving the above object, a first device includes at least one processor, wherein the at least one processor causes the first device to transmit a first frame to a second device on a primary link, and if a second frame in response to the first frame is not received from the second device on the primary link, to perform communication with the second device on a secondary link, wherein each of the first device and the second device supports communication on multiple links including the primary link and the secondary link.

[0020] If the second frame, which is a response to the first frame, is not received from the second device in the primary link, the state of the primary link may be determined to be an interference state or a busy state.

[0021] The at least one processor may further cause the first device to transmit the first frame to the second device on the auxiliary link, and to receive the second frame in response to the first frame from the second device on the auxiliary link, wherein the first frame may be transmitted simultaneously on the primary link and the auxiliary link, or transmission of the first frame on the auxiliary link may be performed when the second frame in response to the first frame is not received on the primary link.

[0022] The second frame received on the auxiliary link may include information indicating that the second device uses the auxiliary link instead of the primary link.

[0023] The second frame received on the auxiliary link may include information indicating a time at which the second device operates on the auxiliary link, and communication between the first device and the second device on the auxiliary link may be performed within the time indicated by the second frame.

[0024] The first frame may be an RTS frame, and the second frame may be a CTS frame.

[0025] According to the present disclosure, an access point (AP) multi-link device (MLD) can support enhanced multi-link single-radio (EMLSR) operation. The AP MLD can detect interference on a primary link, and when interference is detected on the primary link, can operate on a non-primary link (e.g., a secondary link). A station (STA) MLD communicating with the AP MLD may not detect interference on the primary link. When the AP MLD operates on a link other than the primary link, the AP MLD can transmit information indicating the time of operation on the other link. Therefore, the STA MLD can communicate with the AP MLD on the other link based on the information received from the AP MLD even when interference is not detected on the primary link. In a wireless LAN supporting EMLSR, communication between the AP MLD and the STA MLD can be performed smoothly.

[0026] Figure 1 is a conceptual diagram illustrating a first embodiment of a wireless LAN system.

[0027] Figure 2 is a block diagram illustrating a first embodiment of a communication node constituting a wireless LAN system.

[0028] Figure 3 is a conceptual diagram illustrating a first embodiment of a multi-link established between MLDs.

[0029] FIG. 4 is a flowchart illustrating a first embodiment of a negotiation procedure for multi-link operation in a wireless LAN system.

[0030] FIG. 5a is a timing diagram illustrating a first embodiment of a communication method in a wireless LAN supporting EMLSR operation.

[0031] FIG. 5b is a timing diagram illustrating a second embodiment of a communication method in a wireless LAN supporting EMLSR operation.

[0032] Fig. 6 is a timing diagram illustrating a third embodiment of a communication method in a wireless LAN supporting EMLSR operation.

[0033] Fig. 7 is a timing diagram illustrating a fourth embodiment of a communication method in a wireless LAN supporting EMLSR operation.

[0034] This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

[0035] While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component." The term "and / or" encompasses any combination of multiple related items or any one of multiple related items.

[0036] In embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Furthermore, in embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.”

[0037] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0038] The terminology used in this disclosure is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0039] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0040] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding in describing the present disclosure, identical reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0041] Below, a wireless communication system to which embodiments according to the present disclosure are applied will be described. The wireless communication system to which embodiments according to the present disclosure are applied is not limited to the contents described below, and embodiments according to the present disclosure can be applied to various wireless communication systems. The wireless communication system may be referred to as a "wireless communication network." The names of frames proposed in the present disclosure may be generalized, such as first frame, second frame, third frame, etc. In the present disclosure, the transmission time may refer to the start time of frame transmission and / or the end time of frame transmission, and the reception time may refer to the start time of frame reception and / or the end time of frame reception. The time may be interpreted as a time point depending on the context.

[0042] Figure 1 is a conceptual diagram illustrating a first embodiment of a wireless LAN system.

[0043] Referring to FIG. 1, a wireless LAN system may include at least one basic service set (BSS). A BSS refers to a set of stations (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2), STA6, STA7, STA8) that have successfully synchronized and can communicate with each other, and is not a concept that refers to a specific area. In the embodiments below, a station that performs the function of an access point may be referred to as an "access point (AP)", and a station that does not perform the function of an access point may be referred to as a "non-AP station" or a "station."

[0044] A BSS can be divided into an infrastructure BSS and an independent BSS (IBSS). Here, BSS1 and BSS2 may refer to infrastructure BSSs, and BSS3 may refer to an IBSS. BSS1 may include a first station (STA1), a first access point (STA2 (AP1)) providing a distribution service, and a distribution system (DS) connecting multiple access points (STA2 (AP1), STA5 (AP2)). In BSS1, the first access point (STA2 (AP1)) may manage the first station (STA1).

[0045] BSS2 may include a third station (STA3), a fourth station (STA4), a second access point (STA5 (AP2)) providing distribution services, and a distribution system (DS) connecting multiple access points (STA2 (AP1), STA5 (AP2)). In BSS2, the second access point (STA5 (AP2)) may manage the third station (STA3) and the fourth station (STA4).

[0046] BSS3 may refer to an IBSS operating in ad-hoc mode. BSS3 may not have an access point, which is a centralized management entity. In other words, stations (STA6, STA7, STA8) in BSS3 may be managed in a distributed manner. All stations (STA6, STA7, STA8) in BSS3 may be mobile stations, and since they are not permitted to connect to a distribution system (DS), they form a self-contained network.

[0047] Access points (STA2 (AP1), STA5 (AP2)) can provide access to a distributed system (DS) via a wireless medium for stations (STA1, STA3, STA4) associated with them. Communication between stations (STA1, STA3, STA4) in BSS1 or BSS2 is generally performed via access points (STA2 (AP1), STA5 (AP2)), but direct communication between stations (STA1, STA3, STA4) is possible if a direct link is established.

[0048] Multiple infrastructure BSSs can be interconnected via a distribution system (DS). Multiple BSSs connected via a distribution system (DS) are referred to as an extended service set (ESS). Communication nodes within an ESS (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2)) can communicate with each other, and any station (STA1, STA3, STA4) within the same ESS can seamlessly move from one BSS to another while communicating without interruption.

[0049] A distribution system (DS) is a mechanism for an access point to communicate with other access points. According to this mechanism, an access point can transmit frames for stations associated with the BSS it manages, or transmit frames for any station that has moved to another BSS. In addition, an access point can send and receive frames with an external network, such as a wired network. This distribution system (DS) does not necessarily have to be a network, and there are no restrictions on its form as long as it can provide a certain distribution service specified in the IEEE 802.11 standard. For example, the distribution system can be a wireless network such as a mesh network, or a physical structure that connects access points to each other. The communication nodes (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2), STA6, STA7, STA8) included in the wireless LAN system can be configured as follows.

[0050] Figure 2 is a block diagram illustrating a first embodiment of a communication node constituting a wireless LAN system.

[0051] Referring to FIG. 2, a communication node (200) may be an AP, an STA, an AP MLD (multi-link device), an STA MLD, an enhanced multi-link single-radio (EMLSR) AP MLD, or an EMLSR STA MLD. The STA may be a non-AP STA. The operating channel width supported by the AP may be 20 MHz (megahertz), 80 MHz, 160 MHz, etc. The operating channel width supported by the STA may be 20 MHz, 80 MHz, etc. In the present disclosure, an AP may be interpreted as an AP MLD or an EMLSR AP MLD depending on the context, an STA may be interpreted as an STA MLD or an EMLSR STA MLD depending on the context, and an MLD may be interpreted as an AP MLD, an STA MLD, an EMLSR AP MLD, or an EMLSR STA MLD depending on the context. An EMLSR operation may include an MLSR operation. EMLSR can be interpreted as MLSR depending on the context, and MLSR can be interpreted as EMLSR depending on the context. The operation of AP MLD can be interpreted as the operation of AP affiliated with the AP MLD, and the operation of AP can be interpreted as the operation of AP MLD affiliated with the AP. The operation of STA MLD can be interpreted as the operation of STA affiliated with the STA MLD, and the operation of STA can be interpreted as the operation of STA MLD affiliated with the STA.

[0052] A communication node (200) may include at least one processor (210), a memory (220), and a transceiver (230) that is connected to a network and performs communication. The transceiver (230) may be referred to as a transceiver, an RF (radio frequency) unit, an RF module, etc. In addition, the communication node (200) may further include an input interface device (240), an output interface device (250), a storage device (260), etc. Each component included in the communication node (200) may be connected by a bus (270) and communicate with each other.

[0053] However, each component included in the communication node (200) may be connected through an individual interface or individual bus centered around the processor (210), rather than a common bus (270). For example, the processor (210) may be connected to at least one of a memory (220), a transmission / reception device (230), an input interface device (240), an output interface device (250), and a storage device (260) through a dedicated interface.

[0054] The processor (210) can execute program commands stored in at least one of the memory (220) and the storage device (260). The processor (210) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which the methods according to embodiments of the present disclosure are performed. Each of the memory (220) and the storage device (260) may be configured with at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (220) may be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

[0055] FIG. 3 is a conceptual diagram illustrating a first embodiment of a multi-link established between MLDs (multi-link devices).

[0056] Referring to FIG. 3, an MLD may have a single MAC (medium access control) address. In embodiments, the MLD may refer to an AP MLD and / or a non-AP MLD. The MAC address of the MLD may be used in a multi-link setup procedure between the non-AP MLD and the AP MLD. The MAC address of the AP MLD may be different from the MAC address of the non-AP MLD. Access point(s) associated with the AP MLD may have different MAC addresses, and station(s) associated with the non-AP MLD may have different MAC addresses. Access points within the AP MLD with different MAC addresses may be responsible for each link and may function as independent access points (APs).

[0057] Stations within a non-AP MLD with different MAC addresses can be responsible for each link and can act as independent stations (STAs). The non-AP MLD may also be referred to as a STA MLD. The MLD may support STR (simultaneous transmit and receive) operation. In this case, the MLD may perform a transmission operation on link 1 and a reception operation on link 2. An MLD supporting the STR operation may be referred to as an STR MLD (e.g., STR AP MLD, STR non-AP MLD). In embodiments, a link may mean a channel or a band. A device that does not support the STR operation may be referred to as an NSTR (non-STR) AP MLD or an NSTR non-AP MLD (or, an NSTR STA MLD). An AP in an AP MLD may mean an AP associated with an AP MLD. An STA in a STA MLD may mean an STA associated with an STA MLD.

[0058] MLD can transmit and receive frames on multiple links by using a non-contiguous bandwidth expansion scheme (e.g., 80 MHz + 80 MHz). Multi-link operation can include multi-band transmission. AP MLD can include multiple access points, and the multiple access points can operate on different links. Each of the multiple access points can perform the function(s) of the lower MAC layer. Each of the multiple access points can be referred to as a "communication node" or a "subordinate entity." A communication node (e.g., an access point) can operate under the control of a higher layer (or, the processor (210) illustrated in FIG. 2). Non-AP MLD can include multiple stations, and the multiple stations can operate on different links. Each of the multiple stations can be referred to as a "communication node" or a "subordinate entity." A communication node (e.g., a station) can operate under the control of a higher layer (or, the processor (210) illustrated in FIG. 2).

[0059] MLD can perform communications in multiple bands. For example, MLD can perform communications using a 40MHz bandwidth in the 2.4GHz band according to a channel expansion method (e.g., bandwidth expansion method) and can perform communications using a 160MHz bandwidth in the 5GHz band according to a channel expansion method. MLD can perform communications using a 160MHz bandwidth in the 5GHz band and a 160MHz bandwidth in the 6GHz band. One frequency band (e.g., one channel) used by MLD can be defined as one link. Alternatively, multiple links can be established in one frequency band used by MLD. For example, MLD can establish one link in the 2.4GHz band and two links in the 6GHz band. Each link can be referred to as a first link, a second link, a third link, etc. Alternatively, each link can be referred to as link 1, link 2, link 3, etc. The link number can be set by the access point, and an ID (identifier) ​​can be assigned to each link.

[0060] An MLD (e.g., an AP MLD and / or a non-AP MLD) can establish multiple links by performing an access procedure and / or a negotiation procedure for multi-link operation. In this case, the number of links and / or a link to be used among multiple links can be established. A non-AP MLD (e.g., a station) can check information on a band that can communicate with the AP MLD. In the negotiation procedure for multi-link operation between a non-AP MLD and an AP MLD, the non-AP MLD can establish one or more links among the links supported by the AP MLD to be used for multi-link operation. A station that does not support multi-link operation (e.g., an IEEE 802.11a / b / g / n / ac / ax station) can be connected to one or more links among the multiple links supported by the AP MLD.

[0061] When the bandwidth gap between multiple links (e.g., the bandwidth gap between links 1 and 2 in the frequency domain) is sufficient, the MLD can perform simultaneous transmission and reception (STR) operation. For example, the MLD can transmit PPDU (PLCP (physical layer convergence procedure) protocol data unit) 1 using link 1 among the multiple links, and receive PPDU 2 using link 2 among the multiple links. On the other hand, if the bandwidth gap between the multiple links is insufficient and the MLD performs the STR operation, in-device coexistence (IDC) interference, which is interference between the multiple links, may occur. Therefore, if the bandwidth gap between the multiple links is insufficient, the MLD may not be able to perform the STR operation.

[0062] For example, multiple links including link 1, link 2, and link 3 can be established between AP MLD and non-AP MLD 1. If the bandwidth gap between link 1 and link 3 is sufficient, the AP MLD can perform STR operation using link 1 and link 3. In other words, the AP MLD can transmit frames using link 1 and receive frames using link 3. If the bandwidth gap between link 1 and link 2 is not sufficient, the AP MLD may not be able to perform STR operation using link 1 and link 2. If the bandwidth gap between link 2 and link 3 is not sufficient, the AP MLD may not be able to perform STR operation using link 2 and link 3.

[0063] FIG. 4 is a flowchart illustrating a first embodiment of a negotiation procedure for multi-link operation in a wireless LAN system.

[0064] Referring to FIG. 4, the connection procedure between a station (STA) and an access point (AP) in an infrastructure basic service set (BSS) may include a probe step of the access point, an authentication step between the station and the detected access point, and an association step between the station and the authenticated access point.

[0065] In the detection phase, the station can detect one or more access points using either a passive scanning method or an active scanning method. When the passive scanning method is used, the station can detect one or more access points by overhearing beacon frames transmitted by one or more access points. When the active scanning method is used, the station can detect one or more access points by transmitting a probe request frame and receiving a probe response frame, which is a response to the probe request frame, from one or more access points.

[0066] If more than one access point is detected, the station can perform an authentication step with the detected access point(s). In this case, the station can perform the authentication step with multiple access points. Authentication algorithms according to the IEEE 802.11 standard can be classified into open system algorithms that exchange two authentication frames and shared key algorithms that exchange four authentication frames.

[0067] The station can transmit an authentication request frame based on an authentication algorithm according to the IEEE 802.11 standard, and complete authentication with the access point by receiving an authentication response frame, which is a response to the authentication request frame, from the access point.

[0068] When authentication with an access point is completed, the station can perform an association step with the access point. In this case, the station can select one of the access points with which it has performed the authentication step, and perform an association step with the selected access point. That is, the station can transmit an association request frame to the selected access point, and complete the association with the selected access point by receiving an association response frame, which is a response to the association request frame, from the selected access point.

[0069] Meanwhile, multi-link operation may be supported in a wireless LAN system. An MLD may include one or more STAs associated with the MLD. An MLD may be a logical entity. An MLD may be classified into an AP MLD and a non-AP MLD. Each STA associated with an AP MLD may be an AP, and each STA associated with a non-AP MLD may be a non-AP STA. To configure multiple links, a multi-link discovery procedure, a multi-link setup procedure, etc. may be performed. The multi-link discovery procedure may be performed during the detection phase between a station and an access point. In this case, a multi-link information element (ML IE) may be included in a beacon frame, a probe request frame, and / or a probe response frame.

[0070] For example, in order to perform multi-link operation, information indicating whether multi-link operation is available and information about available links may be exchanged between an access point (e.g., an AP associated with an MLD) and a station (e.g., a non-AP STA associated with the MLD) during a detection phase. In a negotiation procedure for multi-link operation (e.g., a multi-link setup procedure), the access point and / or the station may transmit information about links to be used for multi-link operation. The negotiation procedure for multi-link operation may be performed during an association procedure (e.g., an association phase) between a station and an access point, and information element(s) required for multi-link operation may be set or changed by an action frame during the negotiation procedure.

[0071] Additionally, during the connection procedure between a station and an access point (e.g., the association phase), available link(s) of the access point may be established, and each link may be assigned an identifier (ID). Subsequently, during the negotiation and / or change procedures for multi-link operation, information indicating whether each link is active may be transmitted, and this information may be expressed using a link ID.

[0072] Information indicating whether multi-link operation is available can be transmitted and received in a capability information element (e.g., an extremely high throughput (EHT) capability information element) exchange procedure between a station and an access point. The capability information element can include information on a supporting band, information on a supporting link (e.g., an ID and / or number of supporting links), information on links capable of STR operation (e.g., band information of links, spacing information of links), etc. In addition, the capability information element can include information individually indicating links capable of STR operation.

[0073] The present disclosure may be applied to a wireless LAN supporting enhanced multi-link single-radio (EMLSR) operation. The EMLSR operation may refer to the MLSR operation. The AP MLD and the AP supporting the EMLSR operation may be referred to as the EMLSR AP MLD and the EMLSR AP, respectively. The STA MLD and the STA supporting the EMLSR operation may be referred to as the EMLSR STA MLD and the EMLSR STA, respectively.

[0074] FIG. 5a is a timing diagram illustrating a first embodiment of a communication method in a wireless LAN supporting EMLSR operation, and FIG. 5b is a timing diagram illustrating a second embodiment of a communication method in a wireless LAN supporting EMLSR operation.

[0075] Referring to FIGS. 5A and 5B, the AP MLD may operate on a primary link and / or a secondary link (a non-primary link). The STA MLD may operate on a primary link and / or a secondary link. A secondary link may refer to a non-primary link among multiple links. A non-primary link may be referred to as a secondary link, a supplementary link, an auxiliary link, etc. In the present disclosure, a first link may refer to a primary link, and a non-first link (e.g., a second link, a third link, etc.) may refer to a secondary link.

[0076] The primary link can be used for transmitting and receiving control frames and / or management frames. Control frames can include request to send (RTS) frames, clear to send (CTS) frames, acknowledgement (ACK) frames, block ACK (BA) frames, etc. Management frames can include beacon frames, association request frames, association response frames, reassociation request frames, reassociation response frames, probe request frames, probe response frames, authentication request frames, authentication response frames, etc.

[0077] On the primary link, the AP MLD can transmit control frames, including beacon frames, and can also transmit data frames. The secondary link can be used when the primary link is occupied. In other words, the secondary link can be used when the primary link is busy. The secondary link can be used during the period when the primary link is occupied. The secondary link can be used to transmit and receive data frames.

[0078] The STA MLD can perform the function of the AP MLD. The STA MLD performing the function of the AP MLD can be a mobile AP MLD. Alternatively, the mobile AP MLD can be an NSTR AP MLD or an AP MLD performing EMLSR operation. In the present disclosure, the AP MLD can be a mobile AP MLD. The STA MLD can be connected to the AP MLD and can operate on the first link and / or the second link. The AP MLD can be an EMLSR AP MLD or an MLSR AP MLD supporting EMLSR operation. The AP MLD can have a single radio and can operate on the primary link (e.g., the first link) and / or the secondary link (e.g., the second link). An AP associated with the AP MLD (e.g., an EMLSR AP) can operate on one link at a time.

[0079] Alternatively, the AP MLD may have multiple radios (e.g., multiple physical layer (PHY) modules, multiple transceivers, radio frequency (RF) chains, radio chains). An AP MLD having multiple radios may be an enhanced multi-link multi-radio (EMLR) AP MLD or an MLMR AP MLD. Each radio included in the AP MLD may operate on a primary link and / or a secondary link. For example, a first radio of the AP MLD may operate on a primary link, and a second radio of the AP MLD may operate on a secondary link. The operation of each radio of the AP MLD may be interpreted as the operation of the AP MLD on each link. The operation of the AP MLD on each link may be interpreted as the operation of each radio of the AP MLD.

[0080] An AP MLD (e.g., EMLSR AP MLD or EMLMR AP MLD) can operate in a listening mode, waiting for reception of an initial control frame (ICF) from multiple links to receive data frames. The initial control frame can be a specific trigger frame (e.g., a multi-user (MU)-request to send (RTS) trigger frame, a buffer status report poll (BSRP) trigger frame). Alternatively, the initial control frame can be a specific frame other than a trigger frame (e.g., an RTS frame, etc.). When an initial control frame is received in the listening mode, the AP MLD can transition the radio(s) in the listening state to the link on which the initial control frame was received. Thereafter, the AP MLD can receive data frames via multiple spatial streams using all radios. The state of transmitting and receiving the data frames can be referred to as EMLSR mode. Upon completion of receiving the data frame, the AP MLD may wait for a preset period of time before transitioning the radio(s) to multiple links and then waiting for the reception of an initial control frame. In other words, the AP MLD may operate in a listening mode, waiting for the reception of an initial control frame.

[0081] Alternatively, if the primary link is available (e.g., the primary link is not busy), the AP MLD (e.g., EMLSR AP MLD) can transmit and receive data frames using all radios on the primary link without receiving an initial control frame. If the primary link is unavailable (e.g., the primary link is busy or interfered with), the AP MLD (e.g., EMLSR AP MLD) can transmit and receive data frames using all radios on a link other than the primary link (e.g., a secondary link).

[0082] AP 1 operating on a first link and AP 2 operating on a second link may be associated with an AP MLD. STA 1 operating on the first link and STA 2 operating on the second link may be associated with an STA MLD. "If interference is detected on the first link (e.g., the primary link)", "If the first link is occupied by another communication node (e.g., an STA, an AP, an MLD) and the receiving destination of a frame transmitted by the other communication node is not AP 1 of the AP MLD", and / or "If the first link is occupied by another communication node (e.g., an STA, an AP, an MLD) and direct communication (e.g., peer to peer communication) is performed between the other communication nodes", the AP MLD and / or the STA MLD may be operated on the second link (e.g., a link other than the primary link). If interference is detected on the primary link, the AP MLD and / or STA MLD may determine to perform communication on the secondary link. The state of the first link where interference is detected may be an interference state. If "no interference exists on the first link" and / or "the transmission and reception of frames on the first link has been terminated," the AP MLD and / or STA MLD may operate on the first link.

[0083] The channel status can be determined based on at least one of energy detection (ED) clear channel assessment (CCA), virtual CCA based on NAV, or carrier sensing (CS) CCA. The NAV may be set by the LENGTH field and / or the TXOP field of the PPDU preamble. Alternatively, the NAV may be set by the duration field of the MAC header of the MPDU included in the PPDU. The channel status can be determined as an idle state or a busy state. The busy state can be interpreted as the presence of interference in the channel. In other words, the busy state can mean an interference state. Occupancy by another STA can be determined by the virtual CCA.

[0084] AP 1 of the AP MLD can detect interference on its primary link (e.g., the first link). The interference can be caused by a frame (e.g., a data frame) transmitted from an overlapping BSS (OBSS). The AP MLD (e.g., AP 1) can determine the length of an OBSS transmission and the time required for the OBSS transmission by decoding a frame received from the OBSS on the primary link. Decoding the frame can mean at least one of an operation of interpreting the contents of a PPDU preamble or an operation of interpreting the contents of an MPDU. The AP MLD (e.g., AP 2) can operate on a link other than the primary link (e.g., an auxiliary link, a second link) during the time required for an OBSS transmission.

[0085] OBSS transmissions may not be detected by the STA MLD. For example, the STA MLD may not be able to decode the OBSS transmission (e.g., a frame transmitted from the OBSS) and thus may not be able to determine the time taken for the OBSS transmission. The STA MLD may not be able to decode the OBSS transmission, and the energy level of the OBSS transmission may be low. In other words, because the energy level of the OBSS transmission is low, the STA MLD may not be able to detect the OBSS transmission. Similar to the OBSS transmission, the AP MLD may be able to detect the occupation by other STAs, but the STA MLD may not be able to detect the occupation by other STAs. Therefore, the STA MLD may determine that the primary link is available and may therefore attempt to transmit a frame to the AP MLD (e.g., AP 1) on the primary link.

[0086] In the embodiment of FIG. 5A, the STA MLD can transmit RTS frames simultaneously on a first link (e.g., a primary link) and a second link (e.g., a secondary link). The RTS frame can be a multi-user (MU)-RTS frame (e.g., an MU-RTS trigger frame). The RTS frame can be an initial control frame. For example, STA 1 can perform a backoff procedure (e.g., a channel access procedure, an enhanced distributed channel access (EDCA) backoff procedure) on the first link. STA 2 can perform a backoff procedure (e.g., a channel access procedure, an EDCA backoff procedure) on the second link. The backoff procedure of STA 1 and the backoff procedure of STA 2 can succeed simultaneously. The success of the backoff procedure can mean that "the EDCA backoff counter value reaches 0." Alternatively, the backoff procedure of one of STA 1 and STA 2 can succeed first. In this case, one STA may wait without transmitting a frame until the backoff procedure of another STA is successful. The waiting without transmitting a frame may be an operation of maintaining the EDCA backoff counter that has reached 0. If the backoff procedure of another STA is successful, the STAs may transmit frames simultaneously on the first link and the second link. Alternatively, an STA that has successfully performed the backoff procedure may transmit frames regardless of whether the backoff procedure of another STA is successful. In other words, an STA that has successfully performed the backoff procedure may transmit frames immediately. In this case, the transmission start times of the RTS frames transmitted by STA 1 and STA 2 on each link may be different.

[0087] If interference is detected on the first link (e.g., if the first link is busy), the AP MLD may operate on the second link. In this case, AP 1 of the AP MLD may not receive an RTS frame of STA 1 on the first link, and AP 2 of the AP MLD may receive an RTS frame of STA 2 on the second link. AP 2 may transmit a CTS frame to STA 2 in response to the RTS frame. STA 2 may receive the CTS frame from AP 2. After receiving the CTS frame, STA 2 may transmit a data frame to AP 2. AP 2 may receive the data frame from STA 2 and transmit a response frame for the data frame to STA 2. STA 2 may receive a response frame for the data frame from AP 2. In the present disclosure, the response frame may mean an ACK frame or a BA frame. In the present disclosure, an RTS frame may be represented as a first frame, and a CTS frame, which is a response to the RTS frame, may be represented as a second frame.

[0088] STA 1 may transmit an RTS frame, but may not receive a CTS frame in response to the RTS frame. In this case, STA 1 may consider that the frame transmission (e.g., transmission of the RTS frame) has failed. Therefore, STA 1 may increase the value of a backoff parameter (e.g., EDCA backoff parameter). For example, the value of the EDCA backoff parameter may be increased by n times or by m. n may be a natural number. For example, n may be 2. m may be a natural number. For example, m may be 1. The EDCA backoff parameter may include a contention window (CW)[AC(access category)] and / or a quality or service (QoS) short retry counter (QSRC)[AC]. STA 1 may increase the value of CW[AC] by n times and / or increase the value of QSRC[AC] by m. Alternatively, STA 1 may not consider the transmission of the RTS frame on the first link as a failure. In this case, STA 1 may maintain the value of the EDCA backoff parameter. Alternatively, STA 1 may set the value of the EDCA backoff parameter to the initial value.

[0089] In the embodiment of FIG. 5B, the STA MLD (e.g., STA 1) may not detect interference and / or occupancy on the first link (e.g., the primary link). In this case, the STA MLD may determine that the first link is available and may first transmit an RTS frame on the first link. The RTS frame may be an MU-RTS frame (e.g., an MU-RTS trigger frame). The RTS frame may be an initial control frame. For example, STA 1 may perform a backoff procedure (e.g., a channel access procedure, an EDCA backoff procedure) on the first link. If the backoff procedure is successful, STA 1 may transmit a frame (e.g., an RTS frame) on the first link. If "interference is detected on the first link" and / or "the first link is occupied by transmissions from another communication node," the AP MLD may operate on the second link (e.g., the secondary link). Therefore, AP 1 of AP MLD may not receive the RTS frame from STA 1 and may not transmit the CTS frame, which is a response to the RTS frame, to STA 1.

[0090] If a CTS frame from AP 1 is not received on the first link, the STA MLD may transmit an RTS frame (e.g., an MU-RTS frame) to AP 2 on the second link. For example, STA 2 may perform a backoff procedure (e.g., a channel access procedure, an EDCA backoff procedure) on the second link. If the backoff procedure is successful, STA 2 may transmit an RTS frame to AP 2 on the second link. The backoff procedure of the STA MLD may be performed simultaneously on the first link and the second link. While the STA MLD waits for reception of a CTS frame for the RTS frame after transmitting the RTS frame on the first link, the STA MLD may wait without transmitting a frame on the second link even if the backoff procedure is successful on the second link. A success of the backoff procedure may mean that the backoff counter value reaches 0. The behavior of waiting without transmitting a frame may be to keep the EDCA backoff counter reaching 0.

[0091] "If the STA MLD does not receive a CTS frame on the first link and the STA MLD waits for frame transmission while maintaining the backoff counter value as 0 on the second link," the STA MLD may transmit an RTS frame on the second link. In other words, the RTS frame may be transmitted immediately on the second link. If the backoff counter value on the second link has not reached 0, the STA MLD may transmit the RTS frame after the backoff procedure on the second link succeeds.

[0092] STA 1 and STA 2 associated with the STA MLD can perform a backoff procedure simultaneously. If the backoff procedure is successful on the second link, STA 2 can wait for transmission of an RTS frame on the second link until a reception timeout of a CTS frame occurs on the first link. "If a reception timeout of a CTS frame occurs on the first link and the second link remains idle," STA 2 can transmit an RTS frame. Alternatively, if STA 1 does not receive a CTS frame for an RTS frame on the first link within a preset time (e.g., a time corresponding to a CTS reception timer), STA 2 can perform a backoff procedure on the second link from the time of reception timeout of the CTS frame, and transmit the RTS frame after the backoff procedure is successful. If the STA MLD is an EMLSR STA MLD, the EMLSR STA MLD may not perform a frame reception operation while transmitting an RTS frame. In this case, after reception of the CTS frame fails (e.g., after the timeout of the CTS frame reception), the STA MLD can transition all radios to the second link and initiate a backoff procedure on the second link. STA 2 can transmit an RTS frame after the backoff procedure on the second link succeeds. The length of the CTS frame reception timeout and / or the CTS frame reception timer may be longer than PIFS. Alternatively, the length of the CTS frame reception timeout and / or the CTS frame reception timer may be longer than SIFS.

[0093] Alternatively, if the STA MLD operates as an EMLSR STA MLD and the AP MLD operates as an EMLSR AP MLD, the STA MLD may not transition all radios when transmitting an RTS frame, and may transition all radios to the link on which the CTS frame is received from the time point when the CTS frame is detected. Considering the transition time when the STA MLD transitions the radios, the AP MLD may add padding bits (e.g., a padding field) to the CTS frame, and transmit the CTS frame (e.g., a CTS frame including padding bits) to the STA MLD. The STA MLD may receive the CTS frame from the AP MLD, and transmit a frame (e.g., a data frame) through multiple spatial streams using all radios after a short interframe space (SIFS) from the time point when the CTS frame is received.

[0094] The EMLSR STA MLD can perform a backoff procedure on the second link from the time of transmitting the RTS frame on the first link. "If a CTS frame in response to the RTS frame on the first link is not received and the backoff procedure is successful on the second link," STA 2 of the EMLSR STA MLD can transmit an RTS frame on the second link. AP 2 can receive the RTS frame from STA 2. AP 2 can transmit a CTS frame to STA 2 in response to the RTS frame. STA 2 can receive the CTS frame from AP 2 and transmit a data frame to AP 2. AP 2 can receive a data frame from STA 2 and transmit a response frame (e.g., an ACK frame, a BA frame) to STA 2 for the data frame. STA 2 can receive a response frame to the data frame from AP 2.

[0095] If a CTS frame, which is a response to an RTS frame, is not received on the first link, STA 1 may consider the frame transmission as a failure. In this case, STA 1 may increase the value of a backoff parameter (e.g., an EDCA backoff parameter). For example, the value of the EDCA backoff parameter may be increased by a factor of n or may be increased by m. Each of n and m may be a natural number. The EDCA backoff parameter may include CW[AC] and / or QSRC[AC]. STA 1 may increase the value of CW[AC] by a factor of n and may increase the value of QSRC[AC] by m. Alternatively, STA 1 may keep the value of the EDCA backoff parameter as it is. Alternatively, STA 1 may set the value of the EDCA backoff parameter to an initial value.

[0096] The EMLSR AP MLD may not detect interference and / or occupancy, and the STA MLD may detect interference and / or occupancy. If the STA MLD has data to transmit to the EMLSR AP MLD, the STA MLD may perform a backoff procedure on the second link because interference exists on the first link. If the backoff procedure on the second link is successful, the STA MLD may transmit an RTS frame to the AP MLD on the second link. The AP MLD may receive the RTS frame from the STA MLD on the second link, and may transmit a CTS frame in response to the RTS frame on the second link. Thereafter, the AP MLD may receive data frames via multiple spatial streams using all radios on the second link.

[0097] "If data to be transmitted to the STA MLD exists in the EMLSR AP MLD and the first link is determined to be idle," the AP MLD can transmit a data frame on the first link. If a response frame to the data frame on the first link is not received within a preset time, the AP MLD can transition all radios to the second link and transmit the data frame using all radios on the second link.

[0098] Fig. 6 is a timing diagram illustrating a third embodiment of a communication method in a wireless LAN supporting EMLSR operation.

[0099] Referring to FIG. 6, the AP MLD may operate on a primary link and / or a secondary link (a non-primary link). The STA MLD may operate on a primary link and / or a secondary link. A secondary link may refer to a non-primary link among multiple links. A non-primary link may be referred to as a secondary link, a supplementary link, an auxiliary link, etc. In the present disclosure, a first link may refer to a primary link, and a non-first link (e.g., a second link, a third link, etc.) may refer to an auxiliary link.

[0100] The STA MLD can be connected to the AP MLD and can operate on the first link and / or the second link. The AP MLD can be an EMLSR AP MLD or an MLSR AP MLD that supports EMLSR operation. The AP MLD can have a single radio and can operate on the primary link (e.g., the first link) and / or the secondary link (e.g., the second link). An AP associated with an AP MLD (e.g., an EMLSR AP) can operate on one link at a time.

[0101] Alternatively, an AP MLD may have multiple radios (e.g., multiple PHY modules, multiple transceivers, radio frequency (RF) chains, radio chains). An AP MLD having multiple radios may be an EMLMR AP MLD or an MLMR AP MLD. Each radio included in the AP MLD may operate on a primary link and / or a secondary link. For example, a first radio of the AP MLD may operate on a primary link, and a second radio of the AP MLD may operate on a secondary link. The operation of each radio of the AP MLD may be interpreted as the operation of the AP MLD on each link. The operation of the AP MLD on each link may be interpreted as the operation of each radio of the AP MLD.

[0102] An AP MLD (e.g., an EMLSR AP MLD or an EMLMR AP MLD) can operate in a listening mode, waiting for reception of an initial control frame from multiple links to receive a data frame. The initial control frame can be a specific trigger frame (e.g., a multi-user (MU)-request to send (RTS) trigger frame, a buffer status report poll (BSRP) trigger frame). Alternatively, the initial control frame can be a specific frame other than a trigger frame (e.g., an RTS frame, etc.). When an initial control frame is received in the listening mode, the AP MLD can transition the radio(s) in the listening state to the link on which the initial control frame was received. Thereafter, the AP MLD can receive data frames via multiple spatial streams using all radios. The state of transmitting and receiving the data frames can be referred to as an EMLSR mode. Upon completion of reception of the data frame, the AP MLD can wait for a preset period of time before transitioning the radio(s) to the multiple links, and then wait for reception of the initial control frame. In other words, the AP MLD can operate in listening mode, waiting for reception of initial control frames.

[0103] Alternatively, if the primary link is available (e.g., the primary link is not busy), the AP MLD (e.g., EMLSR AP MLD) can transmit and receive data frames using all radios on the primary link. If the primary link is unavailable (e.g., the primary link is busy), the AP MLD (e.g., EMLSR AP MLD) can transmit and receive data frames using all radios on a link other than the primary link (e.g., the secondary link).

[0104] AP 1 operating in a first link and AP 2 operating in a second link may be associated with an AP MLD. STA 1 operating in the first link and STA 2 operating in the second link may be associated with an STA MLD. "If interference is detected in the first link (e.g., the primary link)", "If the first link is occupied by another communication node (e.g., an STA, an AP, an MLD) and the receiving destination of a frame transmitted by the other communication node is not AP 1 of the AP MLD", and / or "If the first link is occupied by another communication node (e.g., an STA, an AP, an MLD) and direct communication (e.g., P2P communication) is performed between the other communication nodes", the AP MLD and / or the STA MLD may be operated in the second link (e.g., a link other than the primary link). In other words, if interference is detected on the primary link, the AP MLD and / or STA MLD may determine to perform communication on the secondary link. The state of the first link where interference is detected may be an interference state. If "no interference exists on the first link" and / or "the transmission and reception of frames on the first link is terminated," the AP MLD and / or STA MLD may operate on the first link.

[0105] The channel status can be determined based on at least one of energy-sensing CCA, virtual CCA based on NAV, or carrier-sensing CCA. The NAV can be set by the length field and / or the TXOP field of the PPDU preamble. Alternatively, the NAV can be set by the duration field of the MAC header of the MPDU included in the PPDU. The channel status can be determined as an idle state or a busy state. The busy state can be interpreted as the presence of interference in the channel. Occupancy by another STA can be determined by the virtual CCA.

[0106] AP 1 of the AP MLD can detect interference on the primary link (e.g., the first link). The interference can be caused by a frame (e.g., a data frame) transmitted from the OBSS. The AP MLD (e.g., AP 1) can determine the length of the OBSS transmission and the time taken for the OBSS transmission by decoding the frame received from the OBSS on the primary link. Decoding the frame can mean at least one of an operation of interpreting the contents of the PPDU preamble or an operation of interpreting the contents of the MPDU. The AP MLD (e.g., AP 2) can operate on a link other than the primary link (e.g., an auxiliary link, a second link) during the time taken for the OBSS transmission.

[0107] OBSS transmissions may not be detected by the STA MLD. For example, the STA MLD may not be able to decode the OBSS transmission (e.g., a frame transmitted from the OBSS) and thus may not be able to determine the time taken for the OBSS transmission. The STA MLD may not be able to decode the OBSS transmission, and the energy level of the OBSS transmission may be low. In other words, because the energy level of the OBSS transmission is low, the STA MLD may not be able to detect the OBSS transmission. Similar to the OBSS transmission, the AP MLD may be able to detect the occupation by other STAs, but the STA MLD may not be able to detect the occupation by other STAs.

[0108] The AP MLD may operate on the secondary link due to interference on the primary link. In this case, the AP MLD may transmit a "frame including information indicating that the AP MLD operates on the secondary link (e.g., a secondary link)" after performing a channel access procedure (e.g., a backoff procedure, an EDCA backoff procedure) on the secondary link. The "frame including information indicating that the AP MLD operates on the secondary link (e.g., a non-primary link)" may be an RTS frame. The RTS frame may be an MU-RTS frame (e.g., an MU-RTS trigger frame). In other words, the RTS frame (e.g., an MU-RTS frame) may indicate that the secondary link is used instead of the primary link. The duration field of the RTS frame (e.g., an MU-RTS frame) may indicate the time that the AP MLD operates on the secondary link. The RTS frame may include information indicating the link on which the AP MLD operates.

[0109] If the RTS frame is an MU-RTS frame, the user info field of the MU-RTS frame may include multiple AIDs (association identifiers). Alternatively, the user info field of the MU-RTS frame may be set to a broadcast AID. The broadcast AID may be an AID indicating all communication nodes (e.g., APs, STAs) or multiple communication nodes. An MU-RTS frame indicating that a secondary link is used may request transmission of a CTS frame as a response to the MU-RTS frame. Alternatively, an MU-RTS frame indicating that a secondary link is used may not request transmission of a CTS frame as a response to the MU-RTS frame.

[0110] An MU-RTS frame (e.g., an MU-RTS frame indicating that an auxiliary link is used) may be a frame indicating TXOP (transmit opportunity) sharing. The MU-RTS frame may include a TXS (TXOP sharing) mode indicating TXOP sharing. In the TXS mode, a plurality of communication nodes (e.g., STAs, APs) indicated by the MU-RTS frame indicating the TXS mode may transmit a frame by performing a backoff procedure (e.g., a channel contention procedure) within the shared TXOP (e.g., a duration indicated by a duration field of the MU-RTS frame or a MAC header). The above operation may be defined in a separate TXS mode. In this case, the TXS mode may be 3. In other words, the operation may be an operation according to TXS mode = 3.

[0111] Alternatively, the "frame including information indicating that the AP MLD operates on the secondary link (e.g., the secondary link)" may be a CTS frame. In other words, the CTS frame may indicate that the secondary link is to be used instead of the primary link. The AP MLD may transmit the CTS frame in response to the RTS frame of the STA MLD. In the embodiments of FIGS. 5A and / or 5B , the CTS frame transmitted by AP 2 of the AP MLD may include information indicating that the secondary link is to be used. The duration field of the CTS frame may indicate the time for which the AP MLD operates on the secondary link (e.g., the secondary link). The CTS frame may include information indicating the link on which the AP MLD operates. The receiver address field of the CTS frame may be set to the address of AP 2 of the AP MLD (e.g., the MAC address), the address of STA 2 of the STA MLD (e.g., the MAC address), or a broadcast address (e.g., a broadcast MAC address).

[0112] Alternatively, a "frame including information indicating that the AP MLD operates on a secondary link (e.g., a secondary link)" may be an action frame. In other words, the action frame may include information indicating that the secondary link is used instead of the primary link. The action field of the action frame may indicate the time when the AP MLD operates on the secondary link (e.g., a secondary link). The action field of the action frame may indicate the link on which the AP MLD operates.

[0113] Alternatively, the "frame including information indicating that the AP MLD operates on a secondary link (e.g., secondary link)" may be a QoS Null frame or a QoS data frame. In other words, the HT (high throughput) control field of the MAC header of the QoS Null frame or the QoS data frame may include information indicating that the secondary link is used. The HT control field may refer to the A-control field. The A-control field may indicate the HT control field. The A-control field may include information indicating the time that the AP MLD operates on the secondary link (e.g., secondary link). The A-control field may include information indicating the link on which the AP MLD operates.

[0114] Alternatively, the "frame including information indicating that the AP MLD operates on a secondary link (e.g., a secondary link)" may be a beacon frame. In other words, the beacon frame may include information indicating that the secondary link is used instead of the primary link. The beacon frame may include information indicating the time that the AP MLD operates on the secondary link (e.g., a secondary link). The beacon frame may include information indicating the link on which the AP MLD operates. The information indicating the time that the AP MLD operates on the secondary link (e.g., a secondary link) and / or the information indicating the link on which the AP MLD operates may be included in the frame body of the beacon frame in the form of at least one of an information element, an element, a subfield, or a field. The "frame including information indicating that the AP MLD operates on the secondary link (e.g., a secondary link)" may be transmitted in a unicast manner, a broadcast manner, or a groupcast manner.

[0115] The STA MLD may receive a "frame including information indicating that the AP MLD operates on a secondary link (e.g., an auxiliary link)". In this case, the STA MLD may transmit and receive frames (e.g., data frames) with the AP MLD during the time indicated by the frame on the secondary link (e.g., the time that the AP MLD operates on the secondary link). The STA MLD may transmit the frame by performing a backoff procedure (e.g., a channel contention procedure) on the secondary link.

[0116] Fig. 7 is a timing diagram illustrating a fourth embodiment of a communication method in a wireless LAN supporting EMLSR operation.

[0117] Referring to FIG. 7, the AP MLD may operate on a primary link and / or a secondary link (a non-primary link). The STA MLD may operate on a primary link and / or a secondary link. A secondary link may refer to a non-primary link among multiple links. A non-primary link may be referred to as a secondary link, a supplementary link, an auxiliary link, etc. In the present disclosure, a first link may refer to a primary link, and a non-first link (e.g., a second link, a third link, etc.) may refer to an auxiliary link.

[0118] The STA MLD can be connected to the AP MLD and can operate on the first link and / or the second link. The AP MLD can be an EMLSR AP MLD or an MLSR AP MLD that supports EMLSR operation. The AP MLD can have a single radio and can operate on the primary link (e.g., the first link) and / or the secondary link (e.g., the second link). An AP associated with an AP MLD (e.g., an EMLSR AP) can operate on one link at a time.

[0119] Alternatively, an AP MLD may have multiple radios (e.g., multiple PHY modules, multiple transceivers, radio frequency (RF) chains, radio chains). An AP MLD having multiple radios may be an EMLMR AP MLD or an MLMR AP MLD. Each radio included in the AP MLD may operate on a primary link and / or a secondary link. For example, a first radio of the AP MLD may operate on a primary link, and a second radio of the AP MLD may operate on a secondary link. The operation of each radio of the AP MLD may be interpreted as the operation of the AP MLD on each link. The operation of the AP MLD on each link may be interpreted as the operation of each radio of the AP MLD.

[0120] AP 1 operating on the first link and AP 2 operating on the second link may be associated with the AP MLD. STA 1 operating on the first link and STA 2 operating on the second link may be associated with the STA MLD. If interference is detected on the first link, the AP MLD and / or the STA MLD may operate on the second link. If interference does not exist on the first link, the AP MLD and / or the STA MLD may operate on the first link.

[0121] The channel state can be determined based on at least one of energy-sensing CCA, virtual CCA based on NAV, or carrier-sensing CCA. The channel state can be determined as an idle state or a busy state. The NAV can be set by the length field and / or the TXOP field of the PPDU preamble. Alternatively, the NAV can be set by the duration field of the MAC header of the MPDU included in the PPDU. The busy state can be interpreted as the presence of interference in the channel. In other words, the busy state can mean an interference state. Occupancy by another STA can be determined by the virtual CCA.

[0122] AP 1 of the AP MLD can transmit a frame on the primary link (e.g., the first link). The PHY preamble of the frame transmitted by AP 1 can include BSS color information. The BSS color of the AP MLD or AP 1 can be 1. Therefore, the BSS color information included in the frame can be 1. The STA MLD can receive the frame from the AP MLD (e.g., AP 1), check the BSS color information included in the frame, and determine that the channel status is set to a busy state by the AP MLD. In other words, it can be determined that the channel status is set to a busy state by the AP MLD to which the STA MLD is connected, not the OBSS. Therefore, the STA MLD can know that the AP MLD is not operating on the second link, and may not perform a transmission operation for the AP MLD on the second link.

[0123] The AP MLD and / or the STA MLD can detect interference on the first link. The interference may be caused by a frame (e.g., a data frame) transmitted from the OBSS. The AP MLD and / or the STA MLD can determine that the interference is caused by OBSS transmission based on BSS color information included in the PHY preamble of the frame received from the OBSS. The interference caused by OBSS transmission may be interference caused by inter-BSS. In other words, inter-BSS interference is OBSS interference. For example, the AP MLD and / or the STA MLD can receive a frame on the first link and determine that the BSS color is not 1 based on the BSS color information included in the frame. In other words, if the identified BSS color is not 1, the STA MLD can determine that the received frame is a frame transmitted by a communication terminal other than the AP MLD to which it is connected.

[0124] Alternatively, if the BSS color is not confirmed, the AP MLD and / or STA MLD may regard the detected interference as interference from the OBSS. Therefore, the AP MLD and / or STA MLD may not operate on the first link and may operate on the second link. In other words, the AP MLD and / or STA MLD may perform communication on the second link.

[0125] The operations of the method according to the embodiments of the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes any type of recording device that stores information readable by a computer system. Furthermore, a computer-readable recording medium can be distributed across network-connected computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

[0126] Additionally, the computer-readable recording medium may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. The program instructions may include not only machine language codes produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

[0127] While some aspects of the present disclosure have been described in the context of a device, they may also represent a description of a corresponding method, wherein a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may also be described as a corresponding block or item or a feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, at least one or more of the most significant method steps may be performed by such a device.

[0128] In embodiments, a programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described herein. In embodiments, the field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. In general, the methods are preferably performed by some hardware device.

[0129] Although the present disclosure has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the claims below.

Claims

1. As a method of the first device, A step of transmitting a first frame to a second device on a primary link; and A step of performing communication with the second device on the auxiliary link if a second frame in response to the first frame on the primary link is not received from the second device, Each of the first device and the second device supports communication in multiple links including the primary link and the secondary link, Method of the first device.

2. In claim 1, If the second frame, which is a response to the first frame, is not received from the second device on the primary link, the state of the primary link is determined to be an interference state or a busy state. Method of the first device.

3. In claim 1, The method of the above first device is, A step of transmitting the first frame to the second device through the auxiliary link; and Further comprising the step of receiving the second frame, which is a response to the first frame, from the second device in the auxiliary link, The first frame is transmitted simultaneously on the primary link and the secondary link, or transmission of the first frame on the secondary link is performed when the second frame, which is a response to the first frame, is not received on the primary link. Method of the first device.

4. In claim 3, The second frame received on the auxiliary link includes information indicating that the second device uses the auxiliary link instead of the primary link. Method of the first device.

5. In claim 3, The second frame received on the auxiliary link includes information indicating the time at which the second device operates on the auxiliary link, Communication between the first device and the second device in the auxiliary link is performed within the time indicated by the second frame. Method of the first device.

6. In claim 1, The first frame is an RTS (request to send) frame, and the second frame is a CTS (clear to send) frame. Method of the first device.

7. As a method of the second device, Step of detecting interference in the primary link; A step of determining that communication is to be performed on an auxiliary link when interference is detected on the primary link; A step of receiving a first frame from a first device in the auxiliary link; and A step of transmitting a second frame in response to the first frame to the first device in the auxiliary link, Each of the first device and the second device supports communication in multiple links including the primary link and the secondary link, Method of the second device.

8. In claim 7, In the above main link, the interference is detected based on CCA (clear channel assessment) or OBSS (overlapping basic service set) transmission. Method of the second device.

9. In claim 7, The second frame includes information indicating that the second device uses the auxiliary link instead of the primary link. Method of the second device.

10. In claim 7, The second frame includes information indicating the time at which the second device operates on the auxiliary link, Communication between the first device and the second device in the auxiliary link is performed within the time indicated by the second frame. Method of the second device.

11. In claim 7, The first frame is an RTS (request to send) frame, and the second frame is a CTS (clear to send) frame. Method of the second device.

12. As the first device, Contains at least one processor, At least one processor of the first device, Transmit the first frame to the second device on the primary link; and If a second frame in response to the first frame is not received from the second device on the primary link, it causes communication with the second device on the secondary link, Each of the first device and the second device supports communication in multiple links including the primary link and the secondary link, First device.

13. In claim 12, If the second frame, which is a response to the first frame, is not received from the second device on the primary link, the state of the primary link is determined to be an interference state or a busy state. First device.

14. In claim 12, At least one processor of the first device, Transmitting the first frame to the second device through the auxiliary link; and further causing the second device to receive the second frame in response to the first frame on the auxiliary link, The first frame is transmitted simultaneously on the primary link and the secondary link, or transmission of the first frame on the secondary link is performed when the second frame, which is a response to the first frame, is not received on the primary link. First device.

15. In claim 14, The second frame received on the auxiliary link includes information indicating that the second device uses the auxiliary link instead of the primary link. First device.

16. In claim 14, The second frame received on the auxiliary link includes information indicating the time at which the second device operates on the auxiliary link, Communication between the first device and the second device in the auxiliary link is performed within the time indicated by the second frame. First device.

17. In claim 12, The first frame is an RTS (request to send) frame, and the second frame is a CTS (clear to send) frame. First device.

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